Total Synthesis of Terpioside B.

The first total synthesis of terpioside B (1) has been accomplished. Key steps include the stereoselective installments of a set of challenging 1,2-cis-glycosidic linkages. Thus, α(1,4)-linked d-galactoside was effectively constructed from a 1,2-anhydrogalactose donor and an unprotected 1,6-anhydrogalactose acceptor by using a boron-mediated aglycon delivery (BMAD) method. In addition, α-l-fucofuranosides were stereoselectively and simultaneously constructed by remote group-assisted 1,2-cis-α-stereoselective glycosylations.

Photo-induced glycosylation using a diaryldisulfide as an organo-Lewis photoacid catalyst.

Photo-induced glycosylations of several acceptors with trichloroacetimidate donors using bis(2-naphthyl)disulfide as an organo-Lewis photoacid (LPA) catalyst proceeded effectively to give the corresponding glycosides in good to high yields. In addition, the ground and excited state absorption spectra of bis(2-naphthyl)disulfide with or without NEt3 suggested the Lewis acidity of bis(2-naphthyl)disulfide upon photo-irradiation.